Abstract
Acetylcholinesterase occurs in the head, midpiece and tail fractions of sonically disrupted bull epididymal spermatozoa. The enzyme exhibits the characteristic substrate concentration optimum; 1.5 x 10-5 [image]-eserine competitively inhibits the hydrolysis of the acetylcholine. The specific activity of the tail fraction is about five times that of the head fraction; in both fractions, the rate of hydrolysis of butyrylcholine is about 15% and of benzoylcholine is about 5 to 8% that of acetylcholine. The enzyme may be involved in the control of coordination and propagation of the flagellar wave.